1. Field of the Invention
The present invention relates to alloys of refractory metals capable of being transformed into homogeneous and pure ingots, and to processes for producing these alloys.
More particularly, it relates to the alloys made from refractory metals having melting temperatures that differ by at least 200.degree. C., such as hafnium-zirconium, hafnium-titanium, niobium-titanium, niobium-zirconium, tantalum-titanium, tantalum-zirconium, tantalum-niobium, niobium-tantalum-titanium, and niobium-titanium-aluminum.
More precisely, these alloys have compositions by weight such that the temperature at which solidification begins is less by at least 150.degree. C. than the solidification temperature of the least meltable metal.
These alloys, initially produced in more or less divided form, are then subjected to at least one melting operation in order to convert them into ingots. The ingots may then be rolled in the form of sheets intended for manufacturing containers for reprocessing nuclear fuel, in the case of the Hf-Zr alloys, or neutron moderators in the case of Hf-Ti alloys, or superconductor compounds or aeronautical superalloys in the case of the Nb-Ti alloy.
2. Description of Related Art
It is known that such alloys can be produced by various processes, such as:
coaluminothermics of oxides, which has the disadvantage of producing alloys that are contaminated with aluminum and oxygen and are in the form of solid blocks that must be crushed before being purified by electronic bombardment and converted into ingots; PA1 coreduction of chlorides by a metal such as sodium or magnesium, which leads to the formation of sponges that are highly polluted with the reducing agent and with iron and chlorine ions, and that also must be crushed; PA1 codeposition from the vapor phase, which produces highly pyrophoric whiskers that are hard to handle and must be compacted prior to melting; PA1 mechanosynthesis or cogrinding of the metals to be alloyed, which leads to particles of relatively coarse particle size that are also highly polluted, and which when melted result in a heterogeneous product because of the presence of unmelted residues of the least meltable metal.